Hydraulic brake pump



Feb. 23, 1943. P. A. SCOTT-[VERSEN 2,311,780

HYDRAULIC BRAKE PUMP Filed May 25', 1942 In v en 601? Patented Feb. 23, 1943 Kenilworth, England, assignor to The Rover Company Limited, C'hesford Grange, near Kenilworth, England Application May 25, 1942, Serial No. 444,472 In Great Britain May 5, 1941 ing' reservoir; The object of the invention is to provide a reciprocatory pump of simple constructionand adapted to establish the required communications between the pump chamber and the replenishing reservoir in a reliable manner. A' further object of the invention is to provide means for controlling the rate of the return movements of the pump plunger;

In the accompanyingsheet of explanatory drawings- Figure 1 is a part sectional elevation of a hydraulic brake pump constructed in accordance with theinvention.

Figure 2' is a sectional side elevation of a modified form of the valve shown in Figure 1.

' Figures 3, 4; and 5 are-respectively a sectional sideelevation, an end elevation, and a perspective view of another modified form of the valve.

In carrying the invention into effect as shown in Figure l, a' hollow-body part a is divided internally by a partition I) to form withinthe body part a pump chamber 0 anda replenishing-reservoir d. The body part a'is adapted to be mounted in an; inclined 'or' vertical position so that the replenishing reservoir d is situated above the pump chamber c. -In a hole in the partition b is arranged a gland 9 through which can slide a closely fitting plunger h in the form of a rod which extends through the replenishing reservoir (1 and is'adapted at its outer end for actuation by the driver, the inner end of the plunger being situated in the pump chamber 0. Actuation of the plunger it may be effected by direct application of foot pressure to a pad i on the outer end of the plunger or to a lever connected to the plunger.

Within the plunger h is formed an axial bore 7' which extends from the inner end of the plunger to any convenient position along the portion within the reservoir d where, by means of a transverse hole is in the plunger, the bore communicates with the reservoir. The inner end of the plunger h is adapted to form a seating m for a non-return valve n in the form of a hollow cap mounted on the inner end of the plunger, the cap having at one end an inturned free edge which engages an annular groove 0 in the periphery of the plunger. The width of the groove 0 is sufficiently greater than the thickness of the inturned free edge of the 5 Claims. (01.1 Bil-54.6)

valve n to permit a limited amount of free axial movement of the valve relatively to the plunger h. Atthe end remote from the inturned free edgethe valve n is adapted to abut against "the seating m on the inner end of the plunger h, and in this end of the valve perforations p are formed to permit liquid to flow from the reservoir at through the valve to the pump chamber 0. Moreover the end of the valven which engages the groove 0 in the plunger h abuts against any convenient abutment (which may be formed by the adjacent surface of the partition b or its gland 9') when the plunger is in its initial position, and so cause the valve to be held open.

Return movement of the plunger h after each operative movement is effected by a spring q acting on and surrounding the portion of the plunger contained within the reservoir d.

The amount of liquid in the reservoir d is sufiicient to keep submerged at all times the portion of the plunger h in which are formed th'e'bore y'and transverse hole 7c above-mentioned', and if desired the level of the liquid in the'reservoir may be maintained by a supply tank connected to the reservoir by a pipe, though usually this latter provisionis not required,and it is usually sufficient to re-charge the reservoir occasionally through a side hole which is normally closed by a cover piece 1.

' When the pump plunger h is moved inwards by the driver, liquid is displaced by the plunger and caused to pass from the pump chamber 0 through an outlet s which is connected by appropriate pipes to the brake operating means in the usual manner. During this movement the valve n is held closed by the liquid pressure in the pump chamber 0. During the return movement of the plunger 71. the valve n remains closed so long as the liquid pressure in the pump chamber c is greater than that exerted on the valve by the liquid in the replenishing reservoir d. But in the event of the pressure in the pump chamber c falling below that in the replenishing reservoir d, as may happen in the event of a very rapid return of the pump plunger h the valve n will open and allow liquid to flow into the pump chamber from the reservoir. This is the condition illustrated in Figure 1. In all conditions, however, just before the plunger it reaches its initial position the valve n is arrested by the above-mentioned abutment in the body part a, and the further small continued movement of the plunger causes the valve and its seating m to be separated, thereby establish ing communication between the reservoir 11 and the pump chamber c.

By means of the construction above described, risk of entry of air to the brake system either at the pump or at the brake operating means is prevented or minimised in a very simple and convenient manner.

When it is desired that the rate of the return movements of plunger h shall be controlled, I arrange the outlet 3 of the pump chamber adjacent to the partition 22. Further, the valve n is made so that it can act as a loosely fitting piston in the pump chamber 0 (which may be of cylindrical form), allowing liquid displaced during the operative movement of the plunger h to pass between its periphery and the surface of the pump chamber to the outlet s. But whilst the clearance between the periphery of the valve n and the pump chamber 0 is not so small as to interfere with the operative movement of the plunger h, itis small enough to enable the valve and the pump chamber to act as a dash pot and retard the return movement of the plunger under the action of the spring q. In the event of the plunger h after depression being released suddenly by the driver, the rate of the return movement under the action of the spring q is controlled by the dash pot action, thus further reducing risk of such a low pressure occurring in the brake system as might result in the undesired inflow of air at any point from the outer atmosphere.

If desired the end of the valve 11. provided with the perforations 21' may also be provided (as shown in Figure 2) with a central hole in which is mounted a rubber or other resilient sealing piece it adapted to bear on the seating surface m.

Instead of having an intumed end which permanently engages the groove 0 in the plunger h, the valve n may be slotted transversely as shown in Figures 3 to 5 so that it can be moved laterally into engagement with the grooved end of the plunger, and when in position within the pump chamber 0 prevented by the inner periphery of this chamber from becoming disengaged from the plunger. In this example the perforations p are obliquely arranged and are situated at opposite sides of an inset rubber or other resilient sealing piece t for co-operating with the seating m.

The invention is not limited to the examples above described as subordinate details of construction may be varied to suit different requirements.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1 A hydraulic brake pump of the kind specified, comprising the combination of a hollow body part divided internally by a partition to form a pump chamber and a replenishing reservoir, the pump chamber having an outlet situated adjacent to the partition, a plunger slidable through the partition and extending through the reservoir, the inner end of the plunger being formed with a passage for establishing communication between the reservoir and pump chamber, a nonretum valve mounted on the inner end of the plunger and adapted by contact with an abutment in the body part to open the said passage when the plunger occupies its initial position, and a spring for efiecting return movement of the plunger, the said valve being adapted to form with the pump chamber a dash pot for controlling the rate of return movement of the plunger.

2. A hydraulic brake pump of the kind specifled, comprising the combination of a hollow body part divided internally by a partition to form a pump chamber and a replenishing reservoir, a plunger slidable through the partition and extending through the reservoir, the inner end of the plunger being formed with a passage for establishing communication between the reservoir and pump chamber, a non-return valve in the form of a cap mounted on and having a limited amount of free axial movement relatively to the inner end of the plunger, the valve being adapted by contact with an abutment in the body part to open the said passage when the plunger occupies its initial position, and a spring for efiecting return movements of the plunger.

3. A hydraulic brake pump as claimed in claim 2, in which the valve is provided with a resilient sealing piece for co-operating with the inner end of the plunger.

4. A hydraulic brake pump as claimed in claim 2, in which the valve is provided with an inturned end engaging a groove in the plunger, the groove being of sufficient Width to allow the required free axial movement of the valve.

5. A hydraulic brake pump as claimed in claim 2, in which the valve is slotted transversely for engagement with the inner end of the plunger, the latter being formed with an annular groove which is engaged by the valve, and disengagement of the valve from the plunger being prevented by the pump chamber in which the valve is situated.

POUL ARNE SCOTT-IVERSEN. 

